Pixel Interpolation

Abstract

An interpolation unit ( 800 ) for computing an output pixel value of an output pixel of an output image on basis of input pixel values of a set of input pixels ( 101 - 114 ) being selected from an input image is disclosed. The interpolation unit ( 800 ) comprises: input pixel selection means ( 802 ) for selecting the input pixels, comprising a first group of pixels ( 101 - 107 ) and a second group of pixels ( 108 - 114 ); and order statistical filtering means ( 804 ) for determining the output pixel value on basis of the set of input pixels ( 101 - 114 ). The set of input pixels is characterized in that lines ( 115, 116 ) connecting pairs of input pixels ( 103, 113 ) being formed by respective input pixels of the first group of pixels ( 101 - 107 ) and the second group of pixels ( 108 - 114 ) intersect at a position ( 100 ) in the particular input image corresponding to a position in the output image where the output pixel is located.

1 . An interpolation unit ( 800 ) for computing an output pixel value of an output pixel of an output image on basis of input pixel values of a set of input pixels ( 101 - 114 ) being selected from a number of input images, which is odd, the interpolation unit ( 800 ) comprising:
 input pixel selection means ( 802 ) for selecting the input pixels, comprising a first group of pixels ( 101 - 107 ) and a second group of pixels ( 108 - 114 ), whereby lines ( 115 , 116 ) connecting pairs of input pixels ( 103 , 113 ) being formed by respective input pixels of the first group of pixels ( 101 - 107 ) and the second group of pixels ( 108 - 114 ) intersect at a position ( 100 ) in a particular input image, corresponding to a position in the output image where the output pixel is located; and   order statistical filtering means ( 804 ) for determining the output pixel value on basis of the set of input pixels ( 101 - 114 ).   
     
     
         2 . An interpolation unit ( 800 ) as claimed in  claim 1 , whereby the order statistical filtering means comprises a central weighted median filter. 
     
     
         3 . An interpolation unit ( 800 ) as claimed in  claim 2 , whereby a first one of the pairs of input pixels ( 104 , 111 ) which is located relatively close to said position ( 100 ) in the particular input image has a relatively high weight compared to a second one of the pairs of input pixels ( 101 - 114 ) which is located relatively far from said position ( 100 ) in the particular input image. 
     
     
         4 . An interpolation unit ( 800 ) as claimed in  claim 1 , whereby the first group of pixels ( 101 - 107 ) are selected from a first row of the particular input image which is located above said position ( 100 ) in the particular input image and the second group of pixels ( 108 - 114 ) are selected from a second row of the particular input image which is located below said position ( 100 ) in the particular input image. 
     
     
         5 . An interpolation unit ( 800 ) as claimed in  claim 1 , whereby the set of input pixels ( 101 - 114 ) comprises further input pixels ( 201 - 207 ) being selected from a previous input image (n−1) being temporally preceding the particular input image (n) and ( 208 - 214 ) from a next input image (n+1) being temporally succeeding the particular input image (n). 
     
     
         6 . An interpolation unit ( 800 ) as claimed in  claim 5 , whereby the further input pixels ( 201 - 207 ) are selected from a first row of the previous input image (n−1) which corresponds to a third row in the particular input image (n) in which said position ( 100 ) is located and selected from a first row of the next input image (n+1) which corresponds to the third row in the particular input image (n). 
     
     
         7 . An interpolation unit ( 800 ) as claimed in  claim 6 , being arranged to compute the output pixel value by computing an average of a first output of a first order statistical filter and a second output of a second order statistical filter. 
     
     
         8 . An interpolation unit ( 800 ) as claimed in  claim 7 , whereby:
 input of the first order statistical filter comprises a first one ( 104 ) of the pixels of the first group of pixels, a first one ( 111 ) of the pixels of the second group of pixels and a first one ( 203 ) of the pixels ( 201 - 207 ) of the first row of the previous input image; and   input of the second order statistical filter comprises the first one ( 104 ) of the pixels of the first group of pixels, the first one ( 111 ) of the pixels of the second group of pixels and a first one ( 212 ) of the pixels ( 208 - 214 ) of the first row of the next input image.   
     
     
         9 . An interpolation unit ( 800 ) as claimed in  claim 8 , whereby the first one ( 203 ) of the pixels ( 201 - 207 ) of the first row of the previous image and the first one ( 212 ) of the pixels ( 208 - 214 ) of the first row of the next image are symmetrically located around said position ( 100 ). 
     
     
         10 . An interpolation unit ( 800 ) as claimed in  claim 7 , whereby the first order statistical filter is a first three-tap median filter and the second order statistical filter is a second three-tap median filter. 
     
     
         11 . An interpolation unit ( 800 ) as claimed in  claim 10 , whereby the first one ( 203 ) of the pixels ( 201 - 207 ) of the first row of the previous input image is selected on basis of minimization of an error criterion. 
     
     
         12 . An image processing apparatus ( 900 ) comprising:
 receiving means ( 902 ) for receiving an image signal representing images; and   an interpolation unit ( 800 ) for computing an output image on basis of input pixel values of a set of input pixels ( 101 - 114 ) being selected from a number of input images, which is odd, the interpolation unit as claimed in  claim 1 .   
     
     
         13 . A method of interpolation by computing an output pixel value of an output pixel of an output image on basis of input pixel values of a set of input pixels ( 101 - 114 ) being selected from a number of input images, which is odd, the method comprising:
 selecting the input pixels, comprising a first group of pixels ( 101 - 107 ) and a second group of pixels ( 108 - 114 ), whereby lines ( 115 , 116 ) connecting pairs of input pixels ( 103 , 113 ) being formed by respective input pixels of the first group of pixels ( 101 - 107 ) and the second group of pixels ( 108 - 114 ) intersect at a position ( 100 ) in a particular input image, corresponding to a position in the output image where the output pixel is located; and   determining the output pixel value by order statistical filtering the set of input pixels ( 101 - 114 ).   
     
     
         14 . A computer program product to be loaded by a computer arrangement, comprising instructions to interpolate an output pixel value of an output pixel of an output image on basis of input pixel values of a set of input pixels ( 101 - 114 ) being selected from a number of input images, which is odd, the computer arrangement comprising processing means and a memory, the computer program product, after being loaded, providing said processing means with the capability to carry out:
 selecting the input pixels, comprising a first group of pixels ( 101 - 107 ) and a second group of pixels ( 108 - 114 ), whereby lines ( 115 , 116 ) connecting pairs of input pixels ( 103 , 113 ) being formed by respective input pixels of the first group of pixels ( 101 - 107 ) and the second group of pixels ( 108 - 114 ) intersect at a position ( 100 ) in a particular input image, corresponding to a position in the output image where the output pixel is located; and   determining the output pixel value by order statistical filtering the set of input pixels ( 101 - 114 ).